U.S. patent number 8,501,837 [Application Number 13/668,403] was granted by the patent office on 2013-08-06 for tire having rubber component containing short fiber reinforcement with compatablizer.
This patent grant is currently assigned to The Goodyear Tire & Rubber Company. The grantee listed for this patent is Martin Paul Cohen, Junling Zhao. Invention is credited to Martin Paul Cohen, Junling Zhao.
United States Patent |
8,501,837 |
Zhao , et al. |
August 6, 2013 |
Tire having rubber component containing short fiber reinforcement
with compatablizer
Abstract
The invention relates to a tire having a rubber component which
contains short fiber reinforcement with a compatabilizer for the
fiber reinforcement. Desirably said short fiber reinforcement is an
aramid pulp. Desirably said compatabilizer is an epoxy
functionalized natural rubber.
Inventors: |
Zhao; Junling (Hudson, OH),
Cohen; Martin Paul (Fairlawn, OH) |
Applicant: |
Name |
City |
State |
Country |
Type |
Zhao; Junling
Cohen; Martin Paul |
Hudson
Fairlawn |
OH
OH |
US
US |
|
|
Assignee: |
The Goodyear Tire & Rubber
Company (Akron, OH)
|
Family
ID: |
45093547 |
Appl.
No.: |
13/668,403 |
Filed: |
November 5, 2012 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20130065984 A1 |
Mar 14, 2013 |
|
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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12971326 |
Dec 17, 2010 |
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Current U.S.
Class: |
523/351 |
Current CPC
Class: |
C08K
7/02 (20130101); C08L 9/06 (20130101); C08L
15/00 (20130101); C08K 7/02 (20130101); C08L
15/00 (20130101); C08L 9/06 (20130101); C08L
2666/08 (20130101); C08L 15/00 (20130101); C08L
2666/08 (20130101); Y10T 152/10513 (20150115) |
Current International
Class: |
C08L
7/00 (20060101) |
Field of
Search: |
;523/351 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Harlan; Robert D.
Attorney, Agent or Firm: Young, Jr.; Henry C.
Claims
What is claimed is:
1. A method of preparing a rubber composition containing at least
one diene-based elastomer, aramid short fibers and epoxidized cis
1,4-polyisoprene rubber where said method is comprised of, based on
parts by weight per 100 parts by weight rubber (phr): (A) preparing
a pre-formed masterbatch comprised of a dispersion of aramid short
fibers in an epoxidized natural cis 1,4-polyisoprene rubber having
an epoxidation in a range of from about 5 to about 60 percent,
followed by (B) blending a sufficient amount of said pre-formed
masterbatch with another rubber composition comprised of at least
one diene-based elastomer other than said epoxidized natural cis
1,4-polyisoprene rubber to provide a rubber composition comprised
of, based on parts by weight per 100 parts by weight elastomers
(phr): (1) 100 phr of diene-based elastomers comprised of: (a)
about 10 to about 95 phr of at elastomers, other than epoxidized
natural cis 1,4-polyisoprene rubber, comprised of at least one of
polymers and copolymers of isoprene and 1,3-butadiene and
copolymers of styrene with at least one of isoprene and
1,3-butadiene as non-functionalized elastomers, and (b) about 5 to
about 100 phr of epoxidized natural cis 1,4-polyisoprene rubber,
and (2) about 30 to about 100 phr of particulate reinforcement
consisting of (a) rubber reinforcing carbon black, or (b) synthetic
amorphous precipitated silica, or (c) combination of rubber
reinforcing carbon black and synthetic amorphous precipitated
silica containing up to about 80 phr of said precipitated silica
together with a silica coupler for said precipitated silica; and
(3) about 0.5 to about 30 phr of said short aramid fibers.
Description
FIELD OF THE INVENTION
The invention relates to a tire having a rubber component which
contains short fiber reinforcement with a compatabilizer for the
fiber reinforcement. Such short fibers may be, for example, aramid
fiber particularly aramid fiber pulp, nylon fiber, polyester fiber
and/or rayon fiber. Desirably said short fiber reinforcement is an
aramid pulp. Such compatabilizer is a functionalized sulfur curable
elastomer such as, for example, epoxidized natural rubber.
BACKGROUND AND PRESENTATION OF THE INVENTION
Pneumatic rubber tires have various rubber components for which
sometimes enhanced stiffness of the rubber composition is a
desirable feature.
Enhanced stiffness of the rubber composition might be accomplished,
for example, by an inclusion of a dispersion of a small content, or
amount, of short fiber reinforcement.
Sometimes aramid short fibers in a form of a pulp are used to
promote an increase of stiffness for a rubber composition, a
practice which is well known by those having skill in such art.
For such practice, where the short fiber is a short aramid fiber
pulp, natural cis 1,4-polyisoprene rubber is used to aid in
dispersing the aramid short fiber pulp in a rubber composition.
For this invention, it is desired to evaluate an effect of
substituting at least a portion of such natural cis
1,4-polyisoprene rubber with a functionalized sulfur curable
elastomer such as, for example, an epoxidized natural rubber
(epoxidized natural cis 1,4-polyisoprene rubber).
A challenge is therefore presented for enhancing short fiber
reinforcement, particularly aramid short fiber pulp reinforcement
of rubber compositions.
In the description of this invention, the terms "rubber" and
"elastomer" where used, are used interchangeably, unless otherwise
prescribed. The terms "rubber composition", "compounded rubber" and
"rubber compound", where used, are used interchangeably to refer to
"rubber which has been blended or mixed with various ingredients"
and the term "compound" relates to a "rubber composition" unless
otherwise indicated. Such terms are well known to those having
skill in the rubber mixing and rubber compounding art.
In the description of this invention, the term "phr" refers to
parts of a respective material per 100 parts by weight of rubber,
or elastomer. The terms "cure" and "vulcanize" are used
interchangeably unless otherwise indicated.
SUMMARY AND PRACTICE OF THE INVENTION
In accordance with this invention, a tire is provided having a
component of a rubber composition containing a dispersion therein
of short organic fibers comprised of, based on parts by weight per
100 parts by weight rubber (phr):
(A) 100 phr of conjugated diene-based elastomers comprised of: (1)
from zero to about 95, alternately from about 10 to about 95, phr
of at least one of polymers and copolymers of isoprene and
1,3-butadiene and copolymers of styrene with at least one of
isoprene and 1,3-butadiene, (non-functionalized elastomers), and
(2) about 5 to about 100, alternately from about 5 to about 90, phr
of a functionalized sulfur curable elastomer as a compatabilizer
for said short organic fibers within said rubber composition
comprised of at least one of polymers and copolymers of isoprene
and 1,3-butadiene and copolymers of styrene with at least one of
isoprene and 1,3-butadiene, preferably comprised of at least one of
functionalized cis 1,4-polyisoprene elastomer and functionalized
styrene/butadiene elastomer (functionalized SBR), with functional
groups interactive with said organic fibers comprised of at least
one of epoxy groups, amine groups (e.g. amine functionalized SBR),
hydroxyl groups (e.g. hydroxyl functionalized SBR), carboxyl
groups, maleic group and maleimide group (e.g. maleated SBR),
preferably epoxy groups and preferably expoxy functionalized
natural cis 1,4-polyisoprene rubber having an epoxidation in a
range of from about 5 to about 60 percent;
(B) about 30 to about 100 phr of particulate reinforcement
comprised of: (1) rubber reinforcing carbon black, or (2) synthetic
amorphous silica (e.g. precipitated silica), or (3) combination of
rubber reinforcing carbon black and synthetic amorphous silica
(e.g. precipitated silica) containing up to about 80 phr of said
precipitated silica together with a silica coupler for said
silica;
(C) about 0.5 to about 30 phr of said short organic fibers wherein
said short organic fibers are comprised of at least one of aramid
fiber (e.g. short aramid fiber pulp), polyester fiber nylon fiber
and rayon fiber, preferably said aramid fiber pulp.
In practice, said rubber composition may also contain up to about
50 phr of at least one of clay and calcium carbonate, alternately
up to about 10 phr of clay and up to about 50 phr of calcium
carbonate.
A purpose of the compatabilizer elastomer is to compatabilize said
organic short fiber, particularly said short aramid fiber pulp,
with said rubber composition.
Accordingly, said short organic fiber may be, for example, short
aramid fiber pulp.
Said compatabilizer elastomer may be, for example, expoxidized cis
1,4-polyisoprene rubber.
In further accordance with this invention, a method of preparing a
rubber composition is comprised of:
(A) mixing said short organic fibers (e.g. said aramid short fiber
pulp) and said compatabilizer elastomer (as a solid compatibilzer
elastomer) with said rubber composition (comprised of solid
elastomer or elastomers) rubber to enable said compatibilzer
elastomer to compatabilize said short organic fibers (e.g. said
aramid short fiber pulp) with said elastomers of said rubber
composition in situ with said rubber composition, or
(B) mixing a pre-formed masterbatch with said rubber composition
wherein said masterbatch is comprised of a dispersion of said
organic short fibers (e.g. said aramid short fiber pulp) blended
with as least one of said functionalized elastomers as a (solid)
functionalized elastomer (e.g. solid epoxidized cis
1,4-polyisoprene rubber or solid functionalized SBR elastomer),
or
(C) mixing a pre-formed masterbatch with said rubber composition
wherein said masterbatch is comprised of at least one of said
organic short fibers (e.g. aramid short fiber pulp) and least one
of said functionalized elastomer as: (1) a coagulated
functionalized elastomer from a latex (aqueous latex) thereof (e.g.
an epoxidized cis 1,4-polyisoprene rubber latex or functionalized
SBR latex), or (2) a recovered functionalized elastomer from an
organic solution thereof (e.g. an epoxidized cis 1,4-polyisoprene
rubber or functionalized SBR).
In additional accordance with this invention, a tire is provided
having a tread comprised of the rubber composition prepared by said
method.
In further accordance with this invention, said method further
comprises preparing a tire with a tread comprised of the rubber
composition prepared by said method.
A significant aspect of this invention is promoting an improved
bonding strength between the short fiber and sulfur cured rubber
matrix through the inclusion of the functionalized elastomer in the
rubber composition, particularly, for example, by use of an
epoxidized natural rubber as a compatabilizer for aramid short
fiber pulp.
This is considered herein to also be significant in a sense of
promoting improved (increased) de-bonding strength between the
short fibers and associated rubber composition and, also for
promoting higher (greater) stiffness of the cured rubber
composition. Various rubber reinforcing carbon blacks might be
used. Representative of various rubber reinforcing blacks are found
in The Vanderbilt Rubber Handbook (1978), Page 417.
In practice, the rubber composition may be prepared, for example,
in at least one preparatory (non-productive) mixing step in an
internal rubber mixer, often a sequential series of at least one,
usually two, separate and individual preparatory internal rubber
mixing steps, or stages, in which the diene-based elastomer is
first mixed with the prescribed silica (if used) and carbon black,
aramid short fibers, and compatabilizer elastomer, or aramid short
fiber masterbatch with said compatabilizer elastomer, followed by a
final mixing step (productive mixing step) in an internal rubber
mixer, or optionally on an open mill mixer, where curatives (sulfur
and sulfur vulcanization accelerators) are blended at a lower
temperature and for a substantially shorter period of time.
It is conventionally required after each internal rubber mixing
step that the rubber mixture (rubber composition) is actually
removed from the rubber mixer and cooled to a temperature below
40.degree. C., perhaps to a temperature in a range of about
20.degree. C. to about 40.degree. C. and then added back to an
internal rubber mixer for the next sequential mixing step, or
stage.
Such non-productive mixing, followed by productive mixing is well
known by those having skill in such art.
The forming of a tire component is contemplated to be by
conventional means such as, for example, by extrusion, or by
calendering, of rubber composition to provide a shaped,
unvulcanized rubber component such as a tire tread layer. Such
forming of a tire tread (layers) is well known to those having
skill in such art.
It is understood that a tire, as a manufactured article, is
prepared by shaping and curing the assembly of its components at an
elevated temperature (e.g. 140.degree. C. to 170.degree. C.) and
elevated pressure in a suitable mold. Such practice is well known
to those having skill in such art.
It is readily understood by those having skill in the pertinent art
that the rubber composition would be compounded by methods
generally known in the rubber compounding art, such as mixing the
various sulfur-vulcanizable constituent rubbers with various
commonly used additive materials, as herein before discussed, such
as, for example, curing aids such as sulfur, activators, retarders
and accelerators, processing additives, such as rubber processing
oils, resins including tackifying resins, silicas, and
plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes,
antioxidants and antiozonants, peptizing agents and reinforcing
materials such as, for example, carbon black. As known to those
skilled in the art, depending on the intended use of the sulfur
vulcanizable and sulfur vulcanized material (rubbers), the
additives mentioned above are selected and commonly used in
conventional amounts.
Typical amounts of fatty acids, if used, which can include stearic
acid, comprise about 0.5 to about 3 phr. Typical amounts of zinc
oxide comprise about 1 to about 5 phr. Typical amounts of waxes
comprise about 1 to about 5 phr. Often microcrystalline waxes are
used. Typical amounts of peptizers comprise about 0.1 to about 1
phr. Typical peptizers may be, for example, pentachlorothiophenol
and dibenzamidodiphenyl disulfide.
The vulcanization is conducted in the presence of a sulfur
vulcanizing agent. Examples of suitable sulfur vulcanizing agents
include elemental sulfur (free sulfur) or sulfur donating
vulcanizing agents, for example, an amine disulfide, polymeric
polysulfide or sulfur olefin adducts. Preferably, the sulfur
vulcanizing agent is elemental sulfur. As known to those skilled in
the art, sulfur vulcanizing agents are used in an amount ranging
from about 0.5 to about 4 phr, or even, in some circumstances, up
to about 8 phr, with a range of from about 1.5 to about 2.5,
sometimes from about 2 to about 2.5, being preferred.
Accelerators are used to control the time and/or temperature
required for vulcanization and to improve the properties of the
vulcanizate. In one embodiment, a single accelerator system may be
used, i.e., primary accelerator. Conventionally and preferably, a
primary accelerator(s) is used in total amounts ranging from about
0.5 to about 4, preferably about 0.8 to about 2.5, phr. In another
embodiment, combinations of a primary and a secondary accelerator
might be used with the secondary accelerator being used in smaller
amounts (of about 0.05 to about 3 phr) in order to activate and to
improve the properties of the vulcanizate. Combinations of these
accelerators might be expected to produce a synergistic effect on
the final properties and are somewhat better than those produced by
use of either accelerator alone. In addition, delayed action
accelerators may be used which are not affected by normal
processing temperatures but produce a satisfactory cure at ordinary
vulcanization temperatures. Vulcanization retarders might also be
used. Suitable types of accelerators that may be used in the
present invention are amines, disulfides, guanidines, thioureas,
thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates.
Preferably, the primary accelerator is a sulfenamide. If a second
accelerator is used, the secondary accelerator is preferably a
guanidine, dithiocarbamate or thiuram compound.
The mixing of the rubber composition can preferably be accomplished
by the aforesaid sequential mixing process. For example, the
ingredients may be mixed in at least two stages, namely, at least
one non-productive (preparatory) stage followed by a productive
(final) mix stage. The final curatives are typically mixed in the
final stage which is conventionally called the "productive" or
"final" mix stage in which the mixing typically occurs at a
temperature, or ultimate temperature, lower than the mix
temperature(s) of the preceding non-productive mix stage(s). The
terms "non-productive" and "productive" mix stages are well known
to those having skill in the rubber mixing art.
The following example is presented to further illustrate the
practice of this invention. The parts and percentages are by weight
unless otherwise indicated.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described by way of example and with
reference to accompanying drawings in which:
FIG. 1 and FIG. 2 graphically present Stress (MPa) versus dynamic
Strain (%) at 23.degree. C. for FIG. 1 and at 150.degree. C. for
FIG. 2 for curves A, B, C, D, E and F for the Samples in Table 2 of
Example I.
FIG. 3 graphically presents hysteresis in term of a hysteresis loop
test at a constant maximum stress of 5 MPa for curves A, B, C, D, E
and F for the Samples in Table 2 of Example I.
FIG. 4 and FIG. 5 are graphical presentations of Stress (MPa)
versus dynamic Strain (%) at test temperature of 23.degree. C. for
FIG. 4 and 150.degree. C. for FIG. 5 for rubber Samples G, H and I
in Table 2 of Example I.
FIG. 6 and FIG. 7 are graphical presentations of Stress (MPa)
versus dynamic Strain (%) for rubber Sample J (Control) and K
(Experimental) at 23.degree. C. and 150.degree. C., respectively,
of Table 7 in Example II.
EXAMPLE I
Rubber compositions were prepared for evaluating an effect of
providing short fiber aramid pulp reinforcement in a rubber
composition together with an epoxy functionalized natural rubber as
a compatibilzer for the short aramid fiber pulp reinforcement.
Control rubber Samples A and B are rubber compositions which
contain natural cis 1,4-polyisoprene rubber (NR) and epoxidized
natural rubber (ENR), respectively, without aramid fiber pulp
reinforcement.
Comparative rubber Sample C contained cis 1,4-polyisoprene natural
rubber with an inclusion of 3 phr of a dispersion of short aramid
fiber pulp reinforcement.
Experimental rubber Samples D, E and F contained epoxidized natural
rubber with an inclusion of 3 phr, 6 phr and 12 phr, respectively,
of short aramid fiber pulp reinforcement.
The rubber compositions were prepared by mixing the ingredients in
sequential non-productive (NP) and productive (PR) mixing steps in
one or more internal rubber mixers.
The basic formulation for the rubber Samples is presented in the
following Table 1 and presented in terms of parts by weight unless
otherwise indicated.
TABLE-US-00001 TABLE 1 Parts Non-Productive Mixing Step (NP),
(mixed to 160.degree. C.) Natural cis 1,4-polyisoprene rubber.sup.1
100 and 0 Epoxidized natural rubber.sup.2 0 and 100
Antioxidant.sup.3 2 Carbon black (N330).sup.4 50 Processing
oil.sup.5 5 Fatty acid.sup.6 3 Zinc oxide 5 Aramid pulp, short
fiber.sup.7 0 and variable Productive Mixing Step (PR), (mixed to
110.degree. C.) Sulfur and sulfur cure accelerators.sup.8 4
.sup.1Natural cis 1,4-polyisoprene rubber .sup.2Expoxidized cis
1,4-polyisoprene rubber as ENR50 .TM., a 50 percent expoxidized
natural rubber from Malaysia company .sup.3Antoxidant of the
diamine type .sup.4Rubber reinforcing carbon black as N330, an ASTM
designation .sup.5Rubber processing oil, primarily aromatic rubber
processing oil .sup.6Fatty acid comprised primarily of stearic acid
and a minor amount of other fatty acids comprised primarily of
palmitic and oleic acids. .sup.7Aramid short fiber pulp (not a
natural rubber/aramid pulp masterbatch) from du Pont de Nemours.
.sup.8Sulfur and sulfur cure accelerators of the sulfenamide and
thiuram types
The rubber Samples were prepared to evaluate the inclusion of short
aramid fiber pulp with the expoxidized natural rubber
compatabilizer, as illustrated in the following Table 2 with the
rubber and aramid fiber pulp reported in terms of parts per 100
parts by weight of rubber (phr) for the rubber Samples A through
F.
Table 2 also reports a summary of various physical properties.
TABLE-US-00002 TABLE 2 Rubber Samples A B C D E F Short aramid
fiber pulp (phr) 0 0 3 3 6 12 Natural cis 1,4-polyisoprene rubber
(phr) 100 0 100 0 0 0 Epoxidized natural rubber (phr) 0 100 0 100
100 100 Summary of Various Physical Properties Rubber Processing
Characteristic RPA.sup.1 100.degree. C., 0.83 Hertz, 15% strain
Uncured rubber, elastic modulus G' (kPa) 153 126 135 107 117 113
Storage Modulus RPA.sup.1, 100.degree. C., 11 Hertz Elastic storage
modulus G' at 1% strain, (kPa) 2688 2072 3002 3326 3825 4266
Percent increase with 3 phr of short aramid fiber -- -- 12 24 -- --
Elastic storage modulus G' at 10% strain, (kPa) 1662 1191 1851 1913
2190 2171 Percent increase with 3 phr of short aramid fiber -- --
12 15 -- -- Tan Delta, RPA.sup.1 100.degree. C., 11 Hertz Tan delta
at 10% strain 0.107 0.175 0.108 0.165 0.160 0.168 Percent increase
with 3 phr of short aramid fiber -- -- 0 54 -- -- .sup.1Rubber
Process Analyzer
From the Summary of Various Physical Properties reported in Table 2
it can be seen that physical interaction of the short aramid fiber
pulp with the ENR (epoxidized natural rubber) containing rubber
composition is considerably greater than with the natural rubber
composition without the expoxidized natural rubber.
This phenomenon can be readily seen that for the rubber
compositions containing 3 phr of the short aramid fiber pulp that
the storage modulus (G') at 1 percent strain increased by 24
percent for the ENR rubber and only 12 percent for the natural
rubber which is indicative of beneficially increased interaction of
the fiber in the ENR rubber composition.
This phenomenon can also be seen for the rubber compositions
containing 3 phr of the short aramid fiber pulp that the storage
modulus (G') at 10 percent strain increased by 15 percent for the
ENR rubber and only 12 percent for the natural rubber which is
indicative of beneficially increased interaction of the fiber in
the ENR rubber composition.
This phenomenon can further be seen for the rubber compositions
containing 3 phr of the short aramid fiber pulp that the Tan delta
property at 10 percent strain increased by 54 percent for the ENR
rubber and virtually no increase in the Tan delta value for the
natural rubber which is further indicative of beneficially
increased interaction of the fiber in the ENR rubber
composition.
In the Drawings
For the physical properties reported for the rubber Samples in the
above Table 2:
(A) FIGS. 1 and 2 graphically present Stress (MPa) versus dynamic
Strain (%) at 23.degree. C. for FIG. 1 and at 150.degree. C. for
FIG. 2.
(B) FIG. 3 graphically presents hysteresis in terms of a hysteresis
loop test at a constant maximum stress of 5 MPa.
In particular, it can be seen from FIG. 1 (Stress versus Strain at
23.degree. C. using an Instron.TM. analytical instrument, ASTM
D412) that, compared to the curves for the natural rubber (curve A)
and the ENR (curve B) that, while the inclusion of 3 phr of the
short aramid fiber in the natural rubber (curve C) increased its
stiffness, namely that it increased the rubber's stress value, the
inclusion of 3 phr of the short aramid fiber in the ENR rubber
(curve D) increased the rubber's stiffness (stress value) by a
significantly greater margin which is indicative of significantly
greater interaction of the short aramid fiber with the ENR
rubber.
It can further be seen from FIG. 1 that, as the loading of the
short aramid fiber in the ENR rubber increased from the 3 phr level
(curve D) to levels of 6 phr (curve E) and 12 phr (curve F), the
stiffness (stress value) of the ENR rubber increased dramatically
to thereby further indicate a greater interaction of the short
aramid fibers with the ENR.
This is considered herein to be significant in a sense that FIG. 1
demonstrates that the interaction of the short aramid fibers had a
significantly greater interaction effect for the ENR than for the
natural rubber composition.
In particular, it can be seen from FIG. 2 (Stress versus Strain at
an increased temperature of 150.degree. C. using an Instron.TM.
analytical instrument, ASTM D412) that, compared to the curves for
the natural rubber (curve A) and the ENR (curve B) that the
inclusion of 3 phr of the short aramid fiber in the natural rubber
(curve C) and in the ENR (curve D) similarly increased their
stiffness values, namely their stress values, the fiber-containing
ENR (curve D) extended further until the rubber sample broke (a
longer curve D line compared to the curve C line) thereby
suggesting a greater elongation durability short aramid
fiber-containing ENR (curve D).
It can further be seen from FIG. 2 that, similar to FIG. 1, as the
loading of the short aramid fiber in the ENR rubber increased from
the 3 phr level (curve D) to levels of 6 phr (curve E) and 12 phr
(curve F), the stiffness (stress value) of the ENR rubber increased
dramatically to thereby further indicate a greater interaction of
the short aramid fibers with the ENR.
It can be seen from FIG. 3 (Hysteresis at Constant Stress of 5 MPa
versus Number of Cycles for the dynamic test) that hysteresis
values for all of the natural rubber (curve A), ENR rubber (curve
B) and 3 phr short aramid fiber containing ENR (curve C), were
significantly higher than hysteresis values for the 3 phr and 6 phr
short aramid fiber containing ENR rubber which is a further
indication of better interaction of the short aramid fibers with
the ENR. The reduction in hysteresis is considered to be a
particularly beneficial effect for the short aramid fiber loaded
ENR rubber in a sense that, as the hysteresis effect is reduced,
significantly beneficially less internal heat build up in the ENR
based rubber composition is expected.
EXAMPLE II
Additional rubber compositions were prepared for evaluating an
effect of providing epoxidized natural rubber as a compatabilizer
for short fiber aramid pulp reinforcement in a rubber composition
comprised of cis 1,4-polybutadiene rubber, natural cis
1,4-polybutadiene rubber and isoprene/butadiene rubber (IBR)
containing 1.6 phr of the aramid short fiber pulp.
Control rubber Sample G contains elastomers composed of cis
1,4-polybutadiene rubber, natural cis 1,4-polyisoprene rubber and
IBR together with reinforcing filler as rubber reinforcing carbon
black without the ENR compatabilizer.
Experimental rubber Samples H and I contained elastomers provided
an inclusion of the 1.6 phr of the short aramid fiber pulp together
with 6 and 12 phr, respectively, of epoxidized natural
compatabilizer for the short aramid fiber pulp.
The rubber compositions were prepared by mixing the ingredients in
sequential non-productive (NP) and productive (PR) mixing steps in
one or more internal rubber mixers.
The basic formulation for the rubber Samples is presented in the
following Table 3 and recited terms of parts by weight unless
otherwise indicated.
TABLE-US-00003 TABLE 3 Parts Non-Productive Mixing Step (NP),
(mixed to 160.degree. C.) Isoprene/butadiene (IBR) rubber.sup.9
36.75 Cis 1,4-polybutadiene rubber.sup.10 36.75 Natural cis
1,4-polyisoprene rubber 26.5, 20.5, 14.5 Epoxidized natural rubber
(ENR50) 0, 6, 12 Antioxidant 3 Carbon black (N550) 51 Resin.sup.11
1.2 Fatty acid 0.5 Zinc oxide 5 Aramid pulp 1.6 Productive Mixing
Step (PR), (mixed to 110.degree. C.) Sulfur and sulfur cure
accelerators 9.5 .sup.9Tin coupled IBR rubber as a 30/70
isoprene/butadiene rubber from The Goodyear Tire and Rubber Company
.sup.10Cis 1,4-polybutadiene rubber as BUD1208 .TM. from The
Goodyear Tire and Rubber Company .sup.11non staining, unreactive
100 percent phenol formaldehyde resin
The rubber Samples were prepared to evaluate the inclusion of short
aramid fiber pulp with the expoxidized natural rubber
compatibilizer, as illustrated in the following Table 4 with the
rubber and aramid fiber pulp reported in terms of parts per 100
parts by weight of rubber (phr) for the rubber Samples G, H, and
I.
TABLE-US-00004 TABLE 4 G H I Natural cis 1,4-polyisoprene rubber
(phr) 26.5 20.5 14.5 Epoxidized natural rubber (phr) 0 6 12 Short
aramid fiber pulp (phr) 1.6 1.6 1.6 Sulfur (phr) 3 3 3 Accelerators
(phr) 6.5 6.5 6.5 Summary of Various Physical Properties Rubber
Processing Characteristic RPA.sup.1 1 00.degree. C., 0.83 Hertz,
15% strain Uncured rubber, elastic modulus G' (kPa) 197 199 213
Elastic Storage Modulus RPA.sup.1 100.degree. C., 11 Hertz Modulus
G', 1% strain (kPa) 3464 3522 3857 Modulus G', 10% strain (kPa)
2781 2789 2991 Tan delta, RPA.sup.1 100.degree. C., 11 Hertz Tan
delta at 10% strain 0.06 0.07 0.08 .sup.1Rubber Process
Analyzer
In Table 4, from the Summary of Various Physical Properties it can
be seen that the cured modulus G' increased progressively for
rubber Samples H and I as the amount of ENR compatabilizer
increased from 6 phr to 12 phr for both the 1 percent and 10
percent test conditions as compared to modulus G' values of 3464
kPa and 2781 kPa, respectively, for rubber Sample G with no ENR
being added.
This is considered herein to be significant in a sense showing the
beneficial effect of the increasing presence of the ENR in the
rubber composition as a compatabilizer for the fiber/rubber
composite to enable an indication of greater filler/rubber
interaction which is a desirable effect.
In the Drawings
For the rubber Samples reported in the above Table 4:
FIGS. 4 and 5 are graphical presentations of Stress (MPa) versus
dynamic Strain (%) at test temperatures of 23.degree. C. and
150.degree. C., respectively, for the aforesaid rubber Samples G, H
and I.
In both FIGS. 4 and 5 Yield "Points" are shown which are
represented by inflections in the curves for each of rubber Samples
G, H and I where the ENR content increased from zero percent
(Sample G) to 6 and 12 phr for Samples H and I, respectively.
In FIG. 4 (23.degree. C. test condition) the Yield Points (cure
inflection regions) progressively and significantly increased with
both higher Stress and Strain values as the ENR contents progressed
from zero (Sample G) to 6 phr (Sample H) to 12 phr (Sample I).
The advancing Yield Points in FIG. 4 (23.degree. C. test condition)
for Samples H and I is indicative of progressively increasing
bonding strength between the short fibers and rubber which is
envisioned as evidence of an increasing fiber/rubber
compatabilizing effect of the increasing ENR content which is a
desirable effect.
Advancing Yield Points in FIG. 5 (150.degree. C. test condition)
can similarly be seen for Samples H and I which is also indicative
of progressively increasing bonding strength between the short
fibers and rubber which is also envisioned as evidence of an
increasing fiber/rubber compatabilizing effect of the increasing
ENR content at the higher temperature which is a desirable
effect.
EXAMPLE III
Use of Aramid Fiber Masterbatch
A fiber masterbatch was prepared by dry blending aramid fiber pulp
and epoxidized natural rubber for use in evaluating an effect of
using epoxidized natural rubber to aid in compatabilizing the
aramid fiber pulp with the rubber composition and to promote
bonding strength to the aramid fibers.
The aramid fiber/epoxidized natural rubber masterbatch is shown in
the following Dry Fiber Masterbatch Table where the amounts are
presented in parts of weight per 100 parts of rubber (phr) unless
otherwise indicated.
TABLE-US-00005 TABLE Dry Fiber Masterbatch Ingredients Dry Fiber
Masterbatch Epoxidized natural rubber (phr) 100 Rubber reinforcing
carbon black (N550) (phr) 60 Aramid short fiber pulp (phr)
26.65
Rubber compositions were prepared for evaluation an effect of
providing short aramid fibers as a pre-formed masterbatch with
epoxidized natural rubber with the epoxidized natural rubber being
used as a compatiblizer for the aramid fiber to promote improved
bonding strength to the aramid fiber.
Control rubber Sample J is prepared without the epoxidized natural
rubber and Experimental rubber Sample K is prepared with a
combination of epoxidized natural rubber and the Fiber Masterbatch
rubber sample.
The rubber Samples were prepared by mixing the ingredients in
sequential non-productive (NP) and productive (P) mixing steps in
internal rubber mixers.
The formulations are shown in the following Table 6 for Samples J
and K with parts and percentages presented in terms of weight
unless otherwise indicated.
TABLE-US-00006 TABLE 6 Basic Formulations J K Non-Productive Mixing
Step (NP) to about 160.degree. C. Isoprene/Butadiene (IBR) rubber
(phr) 36.75 36.75 Cis 1,4-polybutadiene rubber (phr).sup.10 36.75
36.75 Natural cis 1,4-polyisoprene rubber (NR) (phr) 26.5 0
Epoxidized natural rubber (ENR50) (phr) 0 20.5 Antioxidant 4 4
Rubber reinforcing carbon black (N550) 56 47.9 Resin 11 1.2 1.2
Fatty acid 0.5 0.5 Zinc oxide 5 5 Dry Fiber masterbatch 0
11.1.sup.a Productive Mixing Step (P) to about 110.degree. C.
Sulfur 4 3 Sulfur cure accelerator(s) 8 6.5 .sup.aParts by weight
composed of 1.5 phr of fiber, 3.6 phr of carbon black, and 6 phr of
ENR
The following Table 7 illustrates a summary of rubber Samples
followed by a cure behavior as various physical properties of the
Rubber Samples based on the basic formulations presented in
preceding Table 6 with the parts and percentages presented in terms
of weight unless otherwise indicated.
TABLE-US-00007 TABLE 7 J K Epoxidized natural rubber (phr) 0 20.5
Carbon black (N550) (phr) 56 47.9 Fiber Masterbatch (Table 5)
(parts by weight) 0 11.1 Summary of Various Physical Properties
Rubber Processing Characteristic RPA.sup.1 100.degree. C., 0.83
Hertz, 15% strain Uncured rubber, elastic modulus G' (kPa) 204 230
Elastic Storage Modulus RPA.sup.1 100.degree. C., 11 Hertz Modulus
G', 1% strain (kPa) 4569 3857 Modulus G', 10% strain (kPa) 3196
2931 Tan delta, RPA.sup.1 100.degree. C., 11 Hertz Tan delta at 10%
strain 0.1 0.07 K @ P K @ L J With Grain Against Grain
Stress-Strain Test at 23.degree. C. 25% Modulus (MPa) 0.96 1.11
0.88 50% Modulus (MPa) 2.29 3.28 2.71 100% Modulus (MPa) 6.11 9.26
6.86 Tensile strength (MPa) 6.47 14.7 13.7 Elongation at break (%)
104 173 185 Energy at break (J) (joules) 0.43 1.89 1.64
Stress-Strain Test at 150.degree. C. 25% Modulus (MPa) 0.59 0.54
0.47 50% Modulus (MPa) 1.89 2.09 1.88 Tensile strength (MPa) 2.96
5.83 4.84 Elongation at break (%) 68.6 95.3 96.3 Energy at break
(J) (joules) 0.15 0.33 0.29 .sup.1Rubber Process Analyzer
From Table 7 it can be seen that the tensile strength at break
(stress at break) of rubber Sample K, with the masterbatch of ENR
compatiblizer and aramid pulp, increased to a value of over 13 MPa
(13.7 MPa for K@L and 14.7 MPa for K@P), which is an increase of
about 100 percent compared to a value of about 6.5 MPa for rubber
Sample J which did not contain the ENR or fiber/natural rubber
masterbatch.
Elongation at break for rubber Sample K increased to a value of at
least about 170 percent (185 percent for K@L and 173 percent for
K@P), an increase of at least about 66 percent compared to a value
of about 104 percent for rubber Sample J which did not contain the
ENR or fiber/natural rubber masterbatch.
Energy at break at 23.degree. C. for rubber Sample K (prepared with
the pre-formed masterbatch of aramid fiber and ENR) increased to a
value of about 1.9 joules (an increase of about 150 percent) as
compared to a value of about 0.4 joules for rubber Sample J (which
did not contain the inclusion of the pre-formed masterbatch of
aramid fiber and ENR).
These observations are considered herein to be significant as they
are indicative of greater durability of rubber Sample K with the
inclusion of the pre-formed aramid fiber/ENR masterbatch as
compared to rubber Sample J without the aramid fiber/ENR
masterbatch.
In the Drawings
For the rubber Samples reported in the above Table 7:
FIGS. 6 and 7 are graphical presentations of Stress (MPa) and
Strain (%) for rubber Samples J (Control) and K (Experimental) at
23.degree. C. and 150.degree. C., respectively.
The K@L curves in FIGS. 6 and 7 represent Stress versus Strain
curve for the Stress measurement for Experimental rubber Sample K
taken laterally (about 90 degrees or at a right angle) and the K@P
curves for the measurement taken in a parallel direction (about 0
degrees) to its grain.
In the Drawings: For the 23.degree. C. Test Shown in FIG. 6
(A) for Control Rubber Sample J
Control rubber Sample J (without both ENR compatiblizer and short
fiber reinforcement) broke at a strain (elongation) of about 100
percent at a stress (tensile strength) of about 6 MPa, prior to its
intended completion of the tests.
(B) for Experimental Rubber Sample K@P
In contrast, for Experimental rubber Sample K, the K@P Stress value
at about 100 percent strain (where rubber Sample J broke) increased
to about 9.3 MPa without breaking, as reported in Table 7,
representing an increase in Stress value at 100 percent strain, or
elongation, of over 50 percent--without breaking.
Further, Experimental rubber Sample K@P broke at a strain
(elongation) of 173 percent and a stress of about 14.7 MPa, an
increase in strain (elongation) of at least 70 percent and in
ultimate stress, or tensile strength, of over 120 percent, compared
to rubber Sample J.
(C) for Experimental Rubber Sample K@L
In further contrast, for Experimental rubber Sample K, the K@L
Stress value at about 100 percent strain (where rubber Sample J
broke) increased to about 6.9 MPa without breaking, as reported in
Table 7, representing an increase in Stress value at 100 percent
strain, or elongation, of about 15 percent--without breaking.
Further, Experimental rubber Sample K@L broke at a strain
(elongation) of 185 percent and a stress (tensile strength) of
about 13.7 MPa, an increase in strain (elongation) of about 85
percent and in ultimate stress, or tensile strength, of at least
110 percent, compared to rubber Sample J.
In the Drawings: For the 150.degree. C. Test Shown in FIG. 7:
(A) for Control Rubber Sample J
Control rubber Sample J (without both ENR compatiblizer and short
fiber reinforcement) broke at a strain (ultimate elongation at
break) of about 69 percent at a stress (tensile strength) of about
3 MPa, prior to its intended completion of the tests.
(B) for Experimental Rubber Sample K@P
In contrast, for Experimental rubber Sample K, the K@P Stress value
at about 69 percent strain (where rubber Sample J broke) increased
to about 3.4 MPa without breaking, representing an increase in
Stress value at 100 percent strain, or elongation, of about 13
percent--without breaking.
Further, Experimental rubber Sample K@P broke at a strain
(elongation) of about 95 percent and a stress (tensile strength) of
about 5.8 MPa, an increase in strain (elongation) of at least 70
percent and in ultimate stress, or tensile strength, of over 90
percent, compared to rubber Sample J.
(C) for Experimental Rubber Sample K@L
For additional contrast, for Experimental rubber Sample K, the K@L
Stress value at about 70 percent strain (where rubber Sample J
broke) increased to about 3.1 MPa without breaking, as reported in
Table 7, representing an increase in Stress value at 100 percent
strain, or elongation, of about 3 percent--without breaking.
Further, Experimental rubber Sample K@L broke at a strain (ultimate
elongation) of about 96 percent and a stress (tensile strength) of
about 4.8 MPa, an increase in strain (increase in ultimate
elongation at break) of about 39 percent and in ultimate stress, or
tensile strength, of about 60 percent, compared to rubber Sample
J.
These observations are considered herein to be additionally
significant as they are further indicative of greater durability of
rubber Sample K with the inclusion of the pre-formed aramid fiber
masterbatch together with the ENR as compared to rubber Sample J
without the aramid fiber masterbatch and the ENR.
While certain representative embodiments and details have been
shown for the purpose of illustrating the subject invention, it
will be apparent to those skilled in this art that various changes
and modifications can be made therein without departing from the
scope of the subject invention.
* * * * *